| Gill | David | | | Born in Aberdeen, Scotland, June 12, 1843. He is the eldest son of David Gill, of Blairythan, Aberdeenshire; was educated at Marisehall Coll, and University, Aberdeen, erected a private observatory in that city, and applied himself to the study of astronomy and its allied sciences. He undertook the direction of Lord Lindsay's private observatory at Dunecht, near Aberdeen (1872-76); organised Lord Lindsay's Transit of Venus Expedition to Mauritius; made a series of heliometer observations there of the opposition of the minor planet Juno (a new and original method of determining the Solar Parallax), connected the longitudes of Berlin, Malta, Alexandria, Suez, Aden, Seychelles, Mauritius, and Rodriguez, and measured a baseline for the Geodetic Survey of Egypt. In 1877 he organised an expedition to Ascension for determining the Solar Parallax by heliometer observations of the planet Mars. In 1879 he was appointed HM Astronomer at the Cape, and was identified with the well-known work of that institution and the Geodetic Survey of Natal and Cape Colony, the latter work alone, begun in 1883, taking eleven years to accomplish. The accurately determined longitudes on the East and West Coasts of Africa, as well as the longitudes of Mauritius, Reunion, and Seychelles, were established on the initiative and authority of Sir David Gill. In 1885 he commenced the work of photographing all the stars to the 10th magnitude from 18 deg. S to the S Pole, and, with the cooperation of Prof. J C Kapteyn, of Groningen, published three large volumes of Annals of the Cape Observatory showing the places and magnitudes of 454,875 stars. In 1887, in conjunction with Admiral Mouchez, he carried through, an international scheme for photographing the whole sky and cataloguing all stars to the 11th order of magnitude, and Sir David became senior member of the permanent committee, whose reunions he attended at Paris in 1887, 1891, 1896, and 1900. In 1881-83 he conducted a series of determinations of Stellar Parallax, and later another series with the same object—these together form the only determinations of Stellar Parallax in the Southern Hemisphere. In 1888-90 he organised a series of observations of the Minor Planets Iris, Victoria, and Sappho for the determination of the Solar Parallax, all the principal observatories of the world cooperating, and the conclusions as derived by Sir David in his final discussion of the whole series were adopted for use in the nautical almanacs and astronomical ephemerides of all nations at the Paris International Congress in 1896. In that year Sir David Gill was entrusted by the British and German Govts, with the direction of the operations to determine the boundary between British Bechuanaland and German SW Africa, and the necessary survey operations, begun in 1897, are now completed and the results published in a separate volume. He took the initiative in interesting Earl Grey and Mr Rhodes in a Geodetic Survey of Rhodesia, and the project of carrying the work along the 30th meridian from the south to the Mediterranean is already being extended towards Tanganyika under his direction. The execution of the Great African Are of Meridian is perhaps the pet scheme of Sir David's life. Meanwhile, owing to the munificence of Mr Frank McClean, the Cape Observatory has been fitted with a complete equipment for astrophysical research, and Sir David has been able to greatly extend the scope of his operations and the volume of his work, and under his direction the observatory has become by far the most important one in the Southern Hemisphere. | Unknown |
